Fixing the metrics names

[khushbr]

Fixes #: #536

Description of changes: Fixes the metric names in Reader. Minor typos.

Tests: Gradle Build passed.

If new tests are added, how long do the new ones take to complete

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov]

Codecov Report

Merging #537 (b18d45a) into master (7b3cbbd) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##             master     #537      +/-   ##
============================================
+ Coverage     73.69%   73.72%   +0.02%     
- Complexity     2981     2984       +3     
============================================
  Files           362      362              
  Lines         16896    16896              
  Branches       1372     1372              
============================================
+ Hits          12451    12456       +5     
+ Misses         4001     3999       -2     
+ Partials        444      441       -3     

Impacted Files	Coverage Δ	Complexity Δ
...formanceanalyzer/collectors/StatExceptionCode.java	100.00% <100.00%> (ø)	3.00 <0.00> (ø)
...yzer/rca/framework/metrics/RcaVerticesMetrics.java	95.83% <100.00%> (ø)	5.00 <0.00> (ø)
...ormanceanalyzer/reader/ReaderMetricsProcessor.java	78.95% <100.00%> (ø)	76.00 <0.00> (ø)
...ceanalyzer/rca/framework/util/InstanceDetails.java	82.25% <0.00%> (+3.22%)	16.00% <0.00%> (+2.00%)
...ormanceanalyzer/rca/store/rca/cache/CacheUtil.java	65.51% <0.00%> (+3.44%)	11.00% <0.00%> (+1.00%)
...o/elasticsearch/performanceanalyzer/core/Util.java	70.83% <0.00%> (+8.33%)	5.00% <0.00%> (ø%)

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